Shader "UShaderBook/C6/HalfLambert"
{
Properties
    {
        _Diffuse ("Diffuse", Color) = (1,1,1,1)
    }
    SubShader
    {
        Pass{
            Tags {"LightMode"="ForwardBase"}
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "Lighting.cginc"

            fixed4 _Diffuse;

            struct a2v{
                float4 vertex : POSITION;
                float3 normal : NORMAL; 
            };

            struct v2f{
                float4 pos : SV_POSITION;
                fixed3 worldNormal: TEXCOORD0;// 顶点着色器不再需要计算颜色，而是把世界空间法线传给片元着色器
            };

            v2f vert(a2v v){
                v2f o;
                o.pos = UnityObjectToClipPos(v.vertex);

                o.worldNormal = UnityObjectToWorldNormal(v.normal);

                return o;
            }

            float4 frag(v2f i) : SV_TARGET{
                
                fixed3 ambient = UNITY_LIGHTMODEL_AMBIENT.xyz; // 环境光颜色获取
                // fixed3 worldNormal = normalize(mul(v.normal, (float3x3)_Wordl2Object)); // 法线转化为世界法线变换不同于顶点变换
                fixed3 worldNormal = normalize(i.worldNormal);
                fixed3 worldLightDir = normalize(_WorldSpaceLightPos0.xyz); // 光源方向

                fixed3 halfLambert = 0.5 * dot(worldNormal, worldLightDir) + 0.5;
                fixed3 diffuse = _LightColor0.rgb * _Diffuse.rgb * halfLambert;
                fixed3 color = diffuse + ambient;
                return fixed4(color, 1.0);
            }
            ENDCG
        }
    }
    Fallback "Diffuse"
}
